Power companies periodically cut the vegetation that grows along powerline right-of-ways to maintain access to the powerlines and to minimize line losses. Access is required to facilitate service and repair of damaged powerlines. Excessive line losses may occur when high, dense vegetation beneath the powerline causes the electricity flowing through the powerline to bleed into the ground. The higher and more dense the vegetation, the greater the spurious radiation loss from the powerline. Similarly, highway departments periodically cut the vegetation that grows in medians and along roadsides to enhance the safety of motorists and pedestrians. Cutting the vegetation improves visibility and provides a shoulder along the road for emergency stops. As the demand for electrical power and highways increases, the number of right-of-way and roadside miles multiplies exponentially. Accordingly, power companies and highway departments continually seek more efficient and cost effective methods for cutting vegetation along right-of-ways and roadsides.
Power companies and highway departments have discovered that it is advantageous to treat the vegetation at the time it is cut with a treatment to control the growth of unwanted vegetation, or to reduce the rate of growth of desirable vegetation. The vegetation is typically treated with a granular or fluid treatment such as a growth regulator, herbicide, pesticide, fungicide, fertilizer or biological agent, depending on the desired result. The application of a treatment fluid to vegetation is most often accomplished by broadcasting the fluid through the air so that the treatment comes in contact with the vegetation, and is held in place by adhesion of the fluid to the individual plants. The most common methods of broadcasting treatment fluids include spraying the treatment in the area containing the vegetation from an aerial vehicle, from a ground vehicle fitted with a series of spray nozzles, from a hand-held sprayer or from a mower equipped with a treatment applicator. As yet, however, there has not been a mower equipped with a treatment applicator which is capable of cutting vegetation and treating the cut vegetation in a non-horizontal orientation, such as on a hillside using a mower head attached to the end of a hinged boom arm.
Unfortunately, these broadcasting methods do not permit accuracy or control in applying the treatment fluid to the plants. Broadcasting methods, and spraying in particular, allow the treatment to come into contact with desirable plants, and to be applied in areas other than the area to be treated. Once the treatment is broadcast into the air, the spray pattern becomes random and some plants may not be treated at all. Further, when the concentration of the treatment is high, the operator usually applies more treatment than is necessary, and thus substantial amounts of the treatment are wasted. Treatment fluids are typically applied until the foliage of the plant is visibly wet. Thus, there is no way of predicting how much of the treatment will fall onto the ground around the plant where it may contaminate the surrounding soil and the underground water system, and how much, if any, of the treatment will be absorbed into the vascular system, or translocation stream, of the plant where it will produce the desired result.
DowElanco, a manufacturer of herbicides, instructs users that its fluid chemistry is effective only if the treatment penetrates the foliage and is absorbed into the translocation stream of the plant. As a result, chemical companies produce chemicals known as "adjuvants" that enable treatment fluids that are broadcast by spraying to penetrate through dense foliage. Many treatment fluids also include a surfactant to promote absorption of the agent into the translocation stream of the plant. Nevertheless, usually only a small percentage of the volume of treatment fluid that is broadcast by spraying actually reaches the translocation stream of the plant. The remainder of the treatment fluid falls onto the ground where it may mix with precipitation and run onto surrounding land, or may vaporize into the atmosphere and be blown by the wind onto surrounding land.
Naturally, farmers and people living in close proximity to powerline right-of-ways and highways object to the application of treatment fluids which results in run-off or wind drift. Consequently, power companies and highway departments are often restricted by governmental regulations and local ordinances from broadcasting treatment fluids by spraying. Even though the power companies and highway departments regularly heed these regulations and ordinances, environmentalists complain that anytime a treatment fluid is applied by a broadcasting method there is necessarily some contamination of the ground and underground water system, as well as some risk of run-off and wind-drift. Further, in the event that a chemical contamination of the ground or water in the vicinity of the treatment area occurs, the power companies and the highway departments cannot conclusively prove that the cutting and treating operation was not the source of the contamination.